GuzzleHttp to PSR-18 compatible client

[Tuğrul Topuz (tugrul)]

Refactored the HTTP layer to use a PSR-18 compatible client instead of being tightly coupled to Guzzle.

• Replaces direct Guzzle usage with PSR-18 interfaces
• Decouples the library from a specific HTTP client implementation
• Allows consumers to use custom HTTP clients (e.g. Symfony HttpClient) instead of Guzzle
• Improves flexibility and interoperability within the PHP ecosystem

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
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